1. Field of the Invention
This invention relates to an article, e.g. a laminated transparency, and/or a multiple glazed unit, having a sealed layered edge to impede corrosion of a coating at the sealed edge of the article and to a method of making the article, and more particularly, to a laminated transparency and/or multiple glazed unit having a coating containing a metal film, e.g. a sputtered solar control coating and/or heatable coating, and having discontinuities in the metal film at the sealed layered edge to impede corrosion of the metal film at least in a direction inward away from the edge, and to method of making the laminated transparency and/or multiple glazed unit.
2. Discussion of the Technical Issues
Sputtered solar control and/or heatable coatings are applied to substrates, e.g. glass sheets, and the coated substrates are used in the manufacture of articles, e.g. transparencies such as laminated automotive windshields; multiple glazed units or windows for homes, commercial buildings, and windows for storage cases, e.g. windows for refrigerator doors. A common feature of the transparencies is that the transparencies have sealed layered edges. Another common feature of the transparencies is that the coatings usually include one or more sets of a metal film, e.g. a silver film and a dielectric film. Examples of such coatings are discussed in European Patent Application No. 00939609.4. Sputtered coatings are soft coating, compared to pyrolytic coatings, similar to the type disclosed in U.S. Pat. No. 5,464,657, and are usually applied to the surface of the glass sheet designated as an inner surface of the laminate or multiple glazed window.
The usual practice in the manufacture of a laminate is to provide a plastic sheet between a pair of glass sheets with the coating facing one of the surfaces of the plastic sheet and to apply heat and pressure to the glass and plastic sheets to form the laminate. The usual practice in the manufacture of a multiple glazed unit is to position a spacer frame having a layer of moisture impervious adhesive on opposed surfaces of the spacer frame between a pair of glass sheets with a coating facing the spacer frame. The glass sheets are biased toward one another against the spacer frame to flow the adhesive to seal the edges of the unit.
The coating on the marginal edge portions of the sheet in each instance is between the glass sheet and a plastic layer, e.g. the plastic sheet or the layer of moisture impervious adhesive. Moisture in the atmosphere often containing corrosive materials, e.g. acid, attacks the edge of the coating exposed at the periphery of the article, and in particular the edge of the metal film of the coating, and corrodes the metal film. The corrosion of the coating or metal film continues into the sealed layered edge of the article. Minor corrosion of the coating at the sealed marginal edges is unsightly, whereas sever corrosion of the coating at the sealed marginal edges may result in failure of the sealed edge. In the case of a laminate, the failure of the sealed edge may result in delamination of the laminate, and in the case of a multiple glazed unit, the failure of the sealed edge results in air moving into the unit.
The present practice to eliminate corrosion of the coating or metal film of the coating at the sealed layered edges is to provide a coated sheet having uncoated marginal edges. One technique to provide uncoated marginal edges is to mask the marginal edges of the sheet during the coating operation, e.g. as taught in U.S. Pat. No. 5,492,750. Another technique is to coat the complete surface of the sheet and, thereafter, completely remove the coating from the marginal edge portions of the sheet, e.g. as taught in U.S. Pat. No. 4,587,769.
The present techniques are acceptable to prevent corrosion of the coating at the sealed layered edges; however, it would be beneficial to have less expensive techniques available to impede the corrosion of the metal film of the coating at the sealed layered edge of an article.